Removal of microplastics from soils and sludge - New concepts for waste treatment and sludge recycling
We are working on responsible solutions to prevent the distribution of microplastics and micropollutants in our ecosystems. In addition to water treatment, our research and development work in the field of sludge treatment is also advancing.
The reduction of pollutants in sewage sludge and compost prevents their further distribution in soil and water. Targeted and combined removal, education and avoidance strategies can contain and prevent negative consequences such as the impairment of soil ecology and the spread to nearby waters.
Microplastics and micropollutants pollute our process sludge and prevent efficient further use.
With advancing urbanization, solid waste - including biowaste and plastic waste - has been increasing dramatically for many years. It is estimated that around a billion tons of municipal waste are produced worldwide. In contrast, less than 200 million tons are processed in waste incineration plants. Although some plastic waste is recyclable, most of the world's waste is often mixed with other types of household waste and incinerated or landfilled together.
Due to poor management, around 24% of the world's plastic waste is dumped in landfills. A large amount of plastic is buried there. Over time and due to environmental conditions - such as leachate pH (from 4.5 to 9), high salt content, temperature fluctuations, gas formation (e.g., carbon dioxide, methane), physical stress and microbial degradation - smaller and smaller fragments of micro- and nanoplastics and other pollutants arise.
Plastic bags and “compostable plastic bags” as the main problem of bio-waste contamination
Many people do not know that the commercially available organic garbage bags made of "compostable plastic" do not belong in the organic waste bin. A large part of all organic bins contains contaminants such as plastic bags, “compostable plastic bags”, glass, cigarettes and much more that does not belong there.
This mix means that the further use of organic waste as compost is very costly. Conventional processing methods are also not able to completely remove pollutants and micropollutants. They are introduced to fields and gardens via the compost.
Entry paths for microplastics in agricultural soils
The application of sewage sludge and compost as organic fertilizer and the use of foils in vegetable and fruit cultivation are viewed as potential entry routes for microplastics and other micropollutants in agricultural soils.
For example, microplastics from cosmetics, cleaning agents and fiber abrasion are introduced into wastewater when washing synthetic textiles. When treated in sewage treatment plants, some of these particles (the plastics that sink in the water column) end up in the sewage sludge.
Sewage sludge in the cycle
Almost a quarter of the sewage sludge in Germany is applied to the fields as fertilizer, the rest is burned. Treating waste as a resource is a development that can be seen as positive in terms of the circular economy and Cradle2Cradle. To date, there are only a few companies in Germany that use compost or sewage sludge, but the numbers are increasing.
These are mostly arable or specialty farms without their own production of farm manure, which in this way maintain or increase the compost content of their areas.
Points of contact for further research
So far it has been assumed that the spatial distribution of microplastics and micropollutants is very heterogeneous in the landscape.
To be able to make statements about which measures are necessary to avoid the introduction of microplastics and micropollutants into agricultural soils, the extent of the pollution, the effects in the soil and the discharge potential into water bodies have been researched.
An improvement in the quality of the compost would not only mean enormous progress for the circular economy, but one would also pursue sustainable environmental protection and pollutant minimization at the same time and gradually reduce the high concentrations in certain areas.